Extruded Titania-Based Materials Comprising Quaternary Ammonium Compounds and/or Prepared Using Quaternary Ammonium Compounds

ABSTRACT

Porous, extruded titania-based materials further comprising one or more quaternary ammonium compounds and/or prepared using one or more quaternary ammonium compounds, Fischer-Tropsch catalysts comprising them, uses of the foregoing, processes for making and using the same and products obtained from such processes.

The present invention relates to a porous, extruded titania-basedmaterial further comprising one or more quaternary ammonium compoundsand/or prepared using one or more quaternary ammonium compounds,particularly a porous, extruded titanic-based material having improvedcrush strength and being suitable for use as a catalyst support, moreparticularly a Fischer-Tropsch catalyst support. The invention alsorelates to a porous, extruded titania-based material further comprisingone or more quaternary ammonium compounds and/or prepared using one ormore quaternary ammonium compounds, and comprising mesopores andmacropores. The invention further relates to processes for thepreparation of a porous, extruded titania-based material furthercomprising one or more quaternary ammonium compounds and/or preparedusing one or more quaternary ammonium compounds, and processes for theproduction of Fisher-Tropsch synthesis catalysts comprising suchmaterial.

The conversion of synthesis gas into hydrocarbons by the Fischer-Tropschprocess has been known for many years. The growing importance ofalternative energy sources has seen renewed interest in theFischer-Tropsch process as one of the more attractive direct andenvironmentally acceptable routes to high quality transportation fuels.

Many metals, for example cobalt, nickel, iron, molybdenum, tungsten,thorium, ruthenium, rhenium and platinum are known to be catalyticallyactive, either alone or in combination, in the conversion of synthesisgas into hydrocarbons and oxygenated derivatives thereof. Of theaforesaid metals, cobalt, nickel and iron have been studied mostextensively. Generally, the metals are used in combination with asupport material, of which the most common are alumina, silica andcarbon.

In the preparation of metal-containing Fischer-Tropsch catalyst, a solidsupport is typically impregnated with a metal-containing compound, suchas a cobalt-containing compound, which may for instance be anorganometallic or inorganic compound (e.g. Co(NO₃)₂.6H₂O), by contactingwith a solution of the compound. The particular form of metal-containingcompound is generally selected for its ability to form an appropriateoxide (for example Co₃O₄) following a subsequent calcination/oxidationstep. Following generation of the supported metal oxide, a reductionstep is necessary in order to form the pure metal as the activecatalytic species. Thus, the reduction step is also commonly referred toas an activation step.

It is known to be beneficial to perform Fischer-Tropsch catalysis withan extrudate, particularly in the case of fixed catalyst bed reactorsystems. It is, for instance, known that for a given shape of catalystparticles, a reduction in the size of the catalyst particles in a fixedbed gives rise to a corresponding increase in pressure drop through thebed. Thus, the relatively large extrudate particles cause less of apressure drop through the catalyst bed in the reactor compared to thecorresponding powdered or granulated supported catalyst. It has alsobeen found that extrudate particles generally have greater strength andexperience less attrition, which is a particular value in fixed bedarrangements where bulk crush strength may be very high.

An impregnated extrudate may be formed by mixing a solution of ametal-compound with a support material particulate, mulling, andextruding to form an extrudate before drying and calcining.Alternatively, an extrudate of a support material is directlyimpregnated, for instance by incipient wetness, before drying andcalcining.

Commonly used support materials for Fischer-Tropsch catalysts includealumina, silica and carbon; however, a particularly useful material isextruded titania (titanium dioxide). Extruded titania support materialstypically have a mesoporous structure, i.e. the extruded materialcomprises pores having a pore size of 2 to 50 nm.

Titania is also extensively used as a catalyst in the Claus process thatconverts gaseous sulphur compositions into sulphur.

Although titania-based extrudates have been produced on a commercialscale, they generally suffer from poor mechanical (crush) strength,which makes the manufacturing, handling and loading of the catalyst intoa reactor difficult. Moreover, in a fixed reactor, extrudates aresubject to demanding conditions and have to tolerate stress from axialpressure difference, pressure oscillation in the process, surge ofliquid flow, and the weight of catalyst in the upper bed, to list a few.Fracture failure of weak extrudates could cause catastrophic pressuredrop in the process, and the particulates generated from crumbledextrudates could cause dysfunction or malfunction of downstream devicesand equipment. This problem is worsened in extrudates having increasedporosity, as the introduction of additional pores, particularlymacropores, further reduces the crush strength of the extrudates.

Various inorganic binders have been investigated to reinforce thestructure of titania-based extrudates, and these include alumina andalumina-based composites, clays, boric acid, and activated titanic andtitania-based composites.

WO 2007/068731 discloses a process for the preparation of a catalyst orcatalyst precursor, comprising the steps of: (a) admixing: (i) acatalytically active metal or metal compound, (ii) a carrier material,(iii) a gluing agent, and (iv) optionally one or more promoters, and/orone or more co-catalysts; (b) forming the mixture of step (a); anddrying the product of step (b) for more than 5 hours at a temperature upto 100° C. to form the catalyst or catalyst precursor. The catalyticallyactive metal may comprise cobalt, iron or ruthenium, the carriermaterial may comprise titanium, and the forming step may compriseextrusion. The gluing agent may be selected from a wide range ofmaterials, including quaternary ammonium hydroxides, although noexamples of these materials are given. The process specifically excludesa calcining step.

There therefore remains a need for porous, extruded titania-basedmaterial having improved crush strength, particularly a porous, extrudedtitania-based material comprising mesopores and macropores and havingimproved crush strength.

It has now surprisingly been found that incorporating one or morequaternary ammonium compounds, particularly aqueous solutions thereof,during the extrusion of a titania-based material improves the crushstrength of the porous, extruded titanic-based material. Surprisingly,the incorporation of one or more quaternary ammonium compounds in theextrusion process has little impact on the porosity of the finishedsupport, and even when macropores are introduced into the extrudates theuse of one or more quaternary ammonium compounds increases the crushstrength of the macroporous supports.

Thus, in a first aspect the present invention provides a porous,extruded titania-based material further comprising one or morequaternary ammonium compounds, particularly a porous, extrudedtitania-based material comprising mesopores and macropores and furthercomprising one or more quaternary ammonium compounds.

The present invention further provides a process for the preparation ofa porous, extruded titanic-based material having a crush strengthgreater than 3.0 lbf, said process comprising:

a) mixing titanium dioxide and a solution of one or more quaternaryammonium compounds to form a homogenous paste;b) extruding the paste to form an extrudate; andc) drying and/or calcining the extrudate.

The present invention further provides a process for the preparation ofa porous, extruded titania-based material comprising mesopores andmacropores and having a crush strength greater than 3.0 lbf, saidprocess comprising:

a) mixing titanium dioxide and one or more porogens to form a homogenousmixture;b) adding a solution of one or more quaternary ammonium compounds to thehomogenous mixture, and mixing to form a homogenous paste;c) extruding the paste to form an extrudate; andd) drying and/or calcining the extrudate at a temperature sufficient todecompose the one or more porogens.

The present invention yet further provides a porous, extrudedtitania-based material obtainable by a process according to theinvention.

The present invention further provides a Fischer-Tropsch synthesiscatalyst comprising a porous, extruded titania-based material accordingto the invention, and further comprising at least one metal selectedfrom cobalt, iron, nickel, ruthenium or rhodium, particularly aFischer-Tropsch synthesis catalyst comprising a porous, extrudedtitania-based material according to the invention comprising mesoporesand macropores, and further comprising at least one metal selected fromcobalt, iron, nickel, ruthenium or rhodium.

The present invention yet further provides a process for the preparationof a Fischer-Tropsch synthesis catalyst according to the invention, saidprocess comprising:

a) mixing titanium dioxide, a solution of one or more quaternaryammonium compounds and a solution of at least one thermally decomposablecobalt, iron, nickel, ruthenium or rhodium compound, to form ahomogenous paste;b) extruding the paste to form extrudate;c) drying and/or calcining the extrudate at a temperature sufficient toconvert the one or more thermally decomposable cobalt, iron, nickel,ruthenium or rhodium compound to an oxide thereof; or to the metal form;and, where an oxide is formed, optionallyd) heating the dried and/or calcined extrudate under reducing conditionsto convert the one or more cobalt, iron, nickel, ruthenium or rhodiumoxide to the metal form.

The present invention further provides a process for the preparation ofa Fischer-Tropsch synthesis catalyst comprising a porous, extrudedtitania-based material comprising mesopores and macropores according tothe invention, said process comprising:

a) mixing titanium dioxide and one or more porogens to form a homogenousmixture;b) adding a solution of one or more quaternary ammonium compounds and asolution of at least one thermally decomposable cobalt, iron, nickel,ruthenium or rhodium compound to the mixture, and mixing to form ahomogenous paste;c) extruding the paste to form an extrudate;d) drying and/or calcining the extrudate at a temperature sufficient todecompose the one or more porogens and to convert the at least onethermally decomposable cobalt, iron, nickel, ruthenium or rhodiumcompound to an oxide thereof, or to the metal form; and, where an oxideis formed, optionallye) heating the dried and/or calcined extrudate under reducing conditionsto convert the one or more cobalt, iron, nickel, ruthenium or rhodiumoxide to the metal form.

The present invention yet further provides a process for the preparationof a Fischer-Tropsch synthesis catalyst according to the invention, saidprocess comprising:

a) impregnating a porous, extruded titania-based material according tothe invention with a solution of at least one thermally decomposablecobalt, iron, nickel, ruthenium or rhodium compound;b) drying and/or calcining the impregnated porous, extrudedtitania-based material at a temperature sufficient to convert the atleast one thermally decomposable cobalt, iron, nickel, ruthenium orrhodium compound to an oxide thereof or to the metal form; and where anoxide is formed, optionallyc) heating the dried and/or calcined porous, extruded titania-basedmaterial under reducing conditions to convert the at least one cobalt,iron, nickel, ruthenium or rhodium oxide to the metal form.

There is yet further provided a Fischer-Tropsch synthesis catalystobtainable by a process according to the invention, preferably having acrush strength of greater than 5.0 lbf.

There is yet further provided the use of a quaternary ammonium compoundto prepare a porous, extruded titania-based material, preferablycomprising mesopores and macropores, having a crush strength of greaterthan 3.0 lbf, and also the use of a quaternary ammonium compound toprepare a porous, extruded titania-based Fischer-Tropsch synthesiscatalyst, preferably comprising mesopores and macropores, having a crushstrength of greater than 5.0 lbf.

In a further aspect, the present invention provides a process forconverting a mixture of hydrogen and carbon monoxide gases tohydrocarbons, which process comprises contacting a mixture of hydrogenand carbon monoxide with a Fischer-Tropsch synthesis catalyst accordingto the invention or a Fischer-Tropsch synthesis catalyst obtainable by aprocess according to the invention.

In a further aspect, the present invention provides a composition,preferably a fuel composition, comprising hydrocarbons obtained by aprocess according to the invention.

In a further aspect, the present invention provides a process forproducing a fuel composition, said process comprising blendinghydrocarbons obtained by a process according to the invention with oneor more fuel components to form the fuel composition.

The porous, extruded titania-based material according to the presentinvention may be prepared using any quaternary ammonium compound capableof increasing the strength of titania-based extrudates. Without wishingto be bound by theory, it is believed that when titania nanocrystals,particularly anatase and/or rutile polymorphs thereof, are extruded, theparticles formed generally lack cross-linkages based on chemical bondinteractions, and that the forces that hold these particles togetherwhen they are formulated with water are mainly van der Waals forces, butthat activation of the titania particles with one or more quaternaryammonium compounds generates chemical bonding interactions between thesecrystallites, and accordingly substantially improves mechanical strengthof the extrudates, even if all of the quaternary ammonium compounds areremoved during and after extrusion.

Suitable quaternary ammonium compounds for use in the present inventioninclude, but are not limited to, tetramethylammonium hydroxide,tetramethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide and cetyltrimethylammonium hydroxide;particularly tetramethylammonium hydroxide.

As noted above, the improvement in crush strength provided by mixing oneor more quaternary ammonium compounds with titanium dioxide beforeextrusion remains following extrusion, even if the one or morequaternary ammonium compounds is partially or even entirely removedduring and/or after extrusion. Thus, porous, extruded titania-basedmaterials according to the present invention may further comprise one ormore quaternary ammonium compounds, or may be entirely free of suchcompounds. Preferably, the total amount of one or more quaternaryammonium compounds is at least partially reduced in the porous, extrudedtitanic-based material of the present invention compared to the amountpresent during the formation of the material, and more preferably theporous, extruded titania-based material is substantially or entirelyfree of quaternary ammonium compounds.

The one or more quaternary ammonium compounds used in the preparation ofporous, extruded titania-based materials according to the presentinvention may be removed therefrom in any suitable manner, such as bythermal decomposition or oxidation, for example by heating theextrudates to 430° C. or higher, preferably 500° C. or higher.

The total amount of one or more quaternary ammonium compounds used inthe preparation of porous, extruded titania-based materials according tothe present invention may be any amount sufficient to provideimprovements in the crush strength of the finished extrudates, but apreferred range of amounts is from 0.1 to 1.0 mol per gram of titaniumoxide.

The crush strength of the porous, extruded titania-based materialaccording to the present invention may be measured by any suitablemethod known to those skilled in the art, for example using equipmentdesigned to comply with ASTM D4179-01 standards, such as a VarianBenchsaver™ V200 Tablet Hardness Tester. Alternatively, crush strengthmay be measured using equipment designed to comply with ASTM D6175-03standards.

The porous, extruded titania-based material according to the presentinvention suitably has a crush strength of greater than 3.0 lbf,preferably greater than 5.0 lbf, more preferably greater than 8.0 lbf.The upper limit of the crush strength is not critical; however, asuitable maximum crush strength may be 20 lbf. A particularly preferredrange of crush strength for a porous, extruded titania-based materialaccording to the present invention is 3.0 lbf to 20.0 lbf, such as 5.0lbf to 15.0 lbf, 5.0 lbf to 12.0 lbf or 8.0 lbf to 12.0 lbf.

The porous, extruded titania-based material according to the presentinvention generally has a symmetrical geometry that includes, but is notlimited to, cylinders, spheres, spheroids, pastilles, dilobes, such ascylindrical dilobes, trilobes, such as cylindrical trilobes,quadralobes, such as cylindrical quadralobes, and hollow cylinders.

The pore diameter of the porous, extruded titania-based materialaccording to the present invention may be measured by any suitablemethod known to those skilled in the art, for example scanning electronmicroscopy or mercury porosimetry based on mercury intrusion using theWashburn equation with a mercury contacting angle of 130° and a mercurysurface tension of 485 dynes/cm. As used herein, the term “porediameter” equates with “pore size” and consequently refers to theaverage cross-sectional dimension of the pore, understanding, as theskilled person does, that a determination of pore size typically modelspores as having circular cross-sections.

Preferably, the porous, extruded titania-based material comprisingmesopores and macropores according to the present invention, comprises amulti-modal distribution of pores, i.e. the material comprises a rangeof pore sizes/pore diameters with two or more modes, such as two, three,four or more modes. Particularly suitable materials comprise a bi-modaldistribution of pore sizes/pore diameters, i.e. a range of poresizes/pore diameters comprising two modes, the first mode representingmesopores and the second mode representing macropores.

The porous, extruded titanic-based material comprising mesopores andmacropores according to the present invention suitably comprisesmesopores having a pore diameter of 2 to 50 nm, for example 5 to 50 nm,preferably 15 to 45 nm or 20 to 45 nm, more preferably 25 to 40 nm or 30to 40 nm.

The porous, extruded titania-based material comprising mesopores andmacropores according to the present invention suitably comprisesmacropores having a pore diameter of greater than 50 nm, preferably 60to 1000 nm, more preferably 100 to 850 nm.

The pore volume of a porous, extruded titania-based material comprisingmesopores and macropores according to the present invention may bemeasured by any suitable method known to those skilled in the art, forexample using mercury porosimetry.

Suitably, the porous, extruded titania-based material according to thepresent invention has a total pore volume of at least 0.30 ml/g,preferably at least 0.40 ml/g, more preferably at least 0.50 ml/g. Theupper limit of the total pore volume is not critical, so long as thematerial remains sufficiently robust to function as a catalyst support;however, a suitable maximum pore volume may be 1.00 ml/g, preferably0.90 ml/g. Particularly preferred ranges of total pore volume for aporous, extruded titania-based material comprising mesopores andmacropores further comprising zirconium oxide according to the presentinvention are 0.30 to 1.00 ml/g, such as 0.40 to 1.00 ml/g, 0.40 to 0.90ml/g or 0.50 to 0.90 ml/g.

The surface area of the porous, extruded titania-based materialcomprising mesopores and macropores according to the present inventionmay be measured in any suitable way known to those skilled in the art,such as by nitrogen porosimetry using the BET model to the nitrogenadsorption isotherm collected at 77K on a Quadrasorb SI unit(Quantachrome).

Suitably, the porous, extruded titania-based material comprisingmesopores and macropores according to the present invention has asurface area of at least 30 m²/g, preferably at least 40 m²/g. The upperlimit of the surface area is not critical, so long as the material issuitable for the intended use, such as a catalyst support; however, asuitable maximum surface area may be 60 m²/g or 55 m²/g. A particularlysuitable range of surface area for a porous, extruded titania-basedmaterial comprising mesopores and macropores of the present invention is30 to 60 m²/g, preferably 40 to 55 m²/g.

The BET surface area, pore volume, pore size distribution and averagepore radius of a porous, extruded titania-based material comprisingmesopores and macropores may additionally be determined from thenitrogen adsorption isotherm determined at 77K using a MicromeriticsTRISTAR 3000 static volumetric adsorption analyser. A procedure whichmay be used is an application of British Standard method BS4359: Part 1:1984, “Recommendations for gas adsorption (BET) methods” and BS7591:Part 2: 1992, “Porosity and pore size distribution of materials”—Methodof evaluation by gas adsorption. The resulting data may be reduced usingthe BET method (over the relative pressure range 0.05-0.20 P/P₀) and theBarrett, Joyner & Halenda (BJH) method (for pore diameters of 2 to 100nm) to yield the surface area and pore size distribution respectively.Nitrogen porosimetry, such as described above, is the preferred methodfor determining the surface areas of the extruded titania-basedmaterials according to the present invention.

Suitable references for the above data reduction methods are Brunaeur,S, Emmett, P H, and Teller, E; J. Amer. Chem. Soc. 60, 309, (1938) andBarrett, E P, Joyner, L G and Halenda, P P; J Am. Chem. Soc., 1951, 73,375 to 380.

As a further alternative, pore volume may be estimated through mercuryporosimetry by use of an AutoPore IV (Micromeritics) instrument, andpore diameter may be measured from the mercury intrusion branch usingthe Washburn equation with a mercury contacting angle at 130° and amercury surface tension of 485 dynes/cm. Further details are provided inASTM D4284-12 Standard Test Method for Determining Pore VolumeDistribution of Catalysts and Catalyst Carriers by Mercury IntrusionPorosimetry; and Washburn, E. W; The Dynamics of Capillary Flow (1921);Physical Review 1921, 17(3), 273. Mercury porosimetry, such as describedabove, is the preferred method for determining the pore volumes and porediameters of the extruded titania-based materials according to thepresent invention.

The porous, extruded titania-based material according to the presentinvention may be prepared by any suitable extrusion process known tothose skilled in the art, but modified so that one or more quaternaryammonium compounds, preferably an aqueous solution thereof, is mixedwith titanium dioxide before the extrusion step, and, preferably, sothat, after extrusion at least a portion of the one or more quaternaryammonium compounds is removed. Where the porous, extruded titania-basedmaterial according to the present invention comprises mesopores andmacropores, the process is also modified so that one or more porogensare included in the titania-based material during extrusion, and aresubsequently removed by thermal or oxidative decomposition.

The porous, extruded titania-based material according to the presentinvention may be prepared using any suitable form of titanium oxide,such as titanium dioxide (CAS No: 13463-67-7), titanium dioxide anatase(CAS No: 1317-70-0), titanium dioxide rutile (CAS No: 1317-80-2),titanium dioxide brookite (CAS No: 98084-96-9), and admixtures orcomposites thereof.

Where the porous, extruded titania-based material according to thepresent invention is to be used as a catalyst support, it is preferablysubstantially free of extraneous metals or elements which mightadversely affect the catalytic activity of the system. Thus, preferredporous, extruded titania-based materials according to the presentinvention are preferably at least 95% w/w pure, more preferably at least99% w/w pure. Impurities preferably amount to less than 1% w/w, morepreferably less than 0.6% w/w and most preferably less than 0.3% w/w.The titanium oxide from which the porous, extruded titania-basedmaterial is formed is preferably of suitable purity to achieve the abovepreferred purity in the finished extruded product.

In the processes for the preparation of a porous, extruded titania-basedmaterial according to the present invention, titanium dioxide and one ormore quaternary ammonium compounds are mixed to form a homogenous paste.Preferably the one or more quaternary ammonium compounds are mixed withthe titanium dioxide as a solution, most preferably as an aqueoussolution, which may be formed either before the mixing takes places(i.e. by dissolving the one or more quaternary ammonium compounds beforemixing with the titanium dioxide) or during the mixing stage (i.e. bymixing titanium dioxide and one or more quaternary ammonium compoundsand adding a suitable solvent, preferably water). The titanium dioxideand one or more quaternary ammonium compounds may be mixed using anysuitable technique to form a homogenous mixture, such as by mixing in amechanical mixer. If necessary, the wetness of the mixture of titaniumdioxide and one or more quaternary ammonium compounds may be adjusted toform an extrudable paste by adding a liquid extrusion medium. Anysuitable liquid extrusion medium may be used, i.e. any liquid capable ofcausing the titanium dioxide and one or more quaternary ammoniumcompounds to form a homogenous paste suitable for extrusion. Water is anexample of a suitable liquid extrusion medium.

Where the one or more quaternary ammonium compounds is dissolved priorto mixing with titanium dioxide, it may be dissolved at any suitableconcentration, preferably so that all of the one or more quaternaryammonium compounds is dissolved and/or so that when an amount of the oneor more dissolved quaternary ammonium compounds sufficient to providethe required final amount of quaternary ammonium compound is mixed withthe titanium dioxide the mixture will not be too wet to form ahomogenous paste suitable for extrusion. Suitably the one or morequaternary ammonium compounds may be used at a concentration of 0.1mol/litre or above, such as from 0.1 mol/L to 2.0 mol/L, or 0.2 mol/L to1.0 mol/L; preferably 0.5 mol/litre or above.

The porous, extruded titania-based material comprising mesopores andmacropores according to the present invention may be prepared using anysuitable porogen, i.e. a material capable of enabling the formation ofmacropores in an extruded titania-based material once it has beenremoved therefrom, for example by thermal or oxidative decomposition.

Suitable porogens for use in the processes for the production of aporous, extruded titania-based material comprising mesopores andmacropores according to the present invention comprise cellulose orderivatives thereof, such as methyl cellulose (CAS No: 9004-67-5), ethylcellulose (CAS No: 9004-57-3) and ethyl methyl cellulose (CAS No:9004-69-7); alginic acid (CAS No: 9005-32-7) or derivatives thereof,such as ammonium alginate (CAS No: 9005-34-9), sodium alginate (CAS No:9005-38-3) and calcium alginate (CAS No: 9005-35-0); latex, such aspolystyrene latex (CAS No: 26628-22-8) or polyvinylchloride (CAS No:9002-86-2).

The proportion of total porogen to titanium dioxide used in theprocesses of the present invention may be selected so as to provide asuitable proportion of macropores in the porous, extruded titania-basedmaterial. However, a preferred weight ratio of titanium dioxide to totalporogen is from 1:0.1 to 1:1.0, preferably 1:0.1 to 1:0.8, morepreferably 1:0.15 to 1:0.6.

Where a process of the present invention includes mixing one or moreporogens with titanium dioxide to form a homogenous mixture, the porogenmay be mixed with titanium dioxide either before or after mixing withthe one or more quaternary ammonium compounds, or at the same time asthe addition of the one or more quaternary ammonium compounds.Preferably, the titanium dioxide and one or more porogens are mixed toform a homogenous mixture before the addition of the one or morequaternary ammonium compounds to the homogenous mixture. Mixing of thetitanium dioxide and one or more porogens may be carried out in the sameapparatus as the mixing with one or more quaternary ammonium compoundsor in different equipment, as required.

A process for the production of a porous, extruded titania-basedmaterial, according to the present invention may optionally furthercomprise a mulling step to reduce the presence of larger particles thatmay not be readily extruded, or the presence of which would otherwisecompromise the physical properties of the resulting extrudate. Anysuitable mulling or kneading apparatus of which a skilled person isaware may be used for mulling in the context of the present invention.For example, a pestle and mortar may be suitably used in someapplications or a Simpson Muller may suitably be employed. Mulling istypically undertaken for a period of from 3 to 90 minutes, preferablyfor a period of 5 minutes to 30 minutes. Mulling may suitably beundertaken over a range of temperatures, including ambient temperatures.A preferred temperature range for mulling is from 15° C. to 50° C.Mulling may suitably be undertaken at ambient pressures.

The homogenous paste formed in a process for the production of a porous,extruded titania-based material according to the present invention maybe extruded to form an extrudate using any suitable extruding methodsand apparatus of which the skilled person is aware. For example, thehomogenous paste may be extruded in a mechanical extruder (such as aVinci VTE 1) through a die with an array of suitable diameter orifices,such as 1/16 inch diameter, to obtain extrudates with cylindricalgeometry.

The extrudate formed in a process for the production of a porous,extruded titania-based material according to the present invention maybe dried and/or calcined at any suitable temperature. Where the processincludes the incorporation of a porogen before the extrusion step, thedrying and/or calcining is preferably carried out at temperaturessufficient to decompose the one or more porogens.

Where the process of the present invention includes both drying andcalcining, the drying step is preferably carried out before thecalcining step.

Drying in accordance with the present invention is suitably conducted attemperatures of from 50° C. to 150° C., preferably 75° C. to 125° C.Suitable drying times are from 5 minutes to 24 hours. Drying maysuitably be conducted in a drying oven or in a box furnace, for example,under the flow of an inert gas at elevated temperatures.

Preferably, a calcining step is incorporated in the processes of thepresent invention, to ensure that at least a portion, preferably asignificant portion, more preferably substantially all, of the one ormore quaternary ammonium compounds is removed from the finishedextrudates.

Calcination may be performed by any method known to those of skill inthe art, for example in a fluidized bed or a rotary kiln, suitably at atemperature of at least 400° C., such as at least 420° C., morepreferably at least 500° C., and yet more preferably at 500-700° C.

The Fischer-Tropsch synthesis catalyst according to the presentinvention comprises a porous, extruded titania-based material,preferably comprising mesopores and macropores, according to the presentinvention, or obtainable by a process according to the presentinvention, and further comprises at least one metal selected fromcobalt, iron, nickel, ruthenium or rhodium, preferably cobalt. Theamount of metal, on an elemental basis, present in the Fischer-Tropschsynthesis catalyst according to the present invention is suitably from5.0 wt % to 30.0 wt %, preferably 7.0 wt % to 25.0 wt %, more preferably10 wt % to 20 wt %, based on the total weight of the catalyst. As willbe appreciated by the skilled person, the amount of metal, on anelemental basis, present in the Fischer-Tropsch synthesis catalyst maybe readily determined by X-ray fluorescence (XRF) techniques.

The Fischer-Tropsch synthesis catalyst according to the presentinvention may additionally comprise one or more promoters, dispersionaids, binders or strengthening agents. Promoters are typically added topromote reduction of an oxide of metal to pure metal; for example cobaltto cobalt metal, preferably at lower temperatures. Preferably, the oneor more promoters are selected from rhenium, ruthenium, platinum,palladium, molybdenum, tungsten, boron, zirconium, gallium, thorium,manganese, lanthanum, cerium or mixtures thereof. The promoter istypically used in a metal to promoter atomic ratio of up to 250:1, andmore preferably up to 125:1, still more preferably up to 25:1, and mostpreferably 10:1.

The Fischer-Tropsch synthesis catalyst according to the presentinvention may be prepared by incorporating a solution of at least onethermally decomposable cobalt, iron, nickel, ruthenium or rhodiumcompound into a process for the production of a porous, extrudedtitania-based material according to the present invention, i.e. byadding the solution of at least one thermally decomposable cobalt, iron,nickel, ruthenium or rhodium compound at any stage before extrusion ofthe homogenous paste. Preferably, the solution of at least one thermallydecomposable cobalt, iron, nickel, ruthenium or rhodium compound isadded following mixing of the titanium oxide and one or more quaternaryammonium compounds.

Alternatively, a Fischer-Tropsch synthesis catalyst according to thepresent invention may be prepared by impregnating a porous, extrudedtitania-based material, preferably comprising mesopores and macropores,according to the present invention with a solution of at least onethermally decomposable cobalt, iron, nickel, ruthenium or rhodiumcompound. Impregnation of the porous, extruded titania-based materialwith the solution of at least one thermally decomposable cobalt, iron,nickel, ruthenium or rhodium compound in accordance with the presentinvention may be achieved by any suitable method of which the skilledperson is aware, for instance by vacuum impregnation, incipient wetnessor immersion in excess liquid. The impregnating solution may suitably beeither an aqueous solution or a non-aqueous, organic solution of thethermally decomposable metal compound. Suitable non-aqueous organicsolvents include, for example, alcohols, ketones, liquid paraffinichydrocarbons and ethers. Alternatively, aqueous organic solutions, forexample an aqueous alcoholic solution, of the thermally decomposablemetal-containing compound may be employed. Preferably, the solution ofthe thermally decomposable metal-containing compound is an aqueoussolution.

Suitable metal-containing compounds are those which are thermallydecomposable to an oxide of the metal following calcination, or whichmay be reduced directly to the metal form following drying and/orcalcination, and which are completely soluble in the impregnatingsolution. Preferred metal-containing compounds are the nitrate, acetateor acetyl acetonate salts of cobalt, iron, nickel, ruthenium or rhodium,most preferably the nitrate, for example cobalt nitrate hexahydrate.

Following extrusion, the extrudate may be dried and/or calcined at atemperature sufficient to convert the at least one thermallydecomposable cobalt, iron, nickel, ruthenium or rhodium compound to anoxide thereof or to the metal form.

Following impregnation, the impregnated extrudate may be dried and/orcalcined at a temperature sufficient to convert the at least onethermally decomposable cobalt, iron, nickel, ruthenium or rhodiumcontaining compound to an oxide thereof or to the metal form.

The drying and calcining temperatures and conditions suitable forproducing a porous, extruded titania-based material according to thepresent invention are also suitable for use in the processes forpreparing Fischer-Tropsch synthesis catalysts according to the presentinvention.

Where an oxide of cobalt, iron, nickel, ruthenium or rhodium is formedduring a process for the preparation of a Fischer-Tropsch synthesiscatalyst according to the present invention, the material may be used asa catalyst in a Fischer-Tropsch reaction without further processing, andthe oxide of cobalt, iron, nickel, ruthenium or rhodium will beconverted to the metal form during such use. Alternatively, the materialcomprising an oxide of cobalt, iron, nickel, ruthenium or rhodium mayoptionally be heated under reducing conditions to convert the at leastone cobalt, iron, nickel, ruthenium or rhodium oxide to the metal formbefore use as a Fischer-Tropsch synthesis catalyst. Any suitable meansfor converting the oxide of cobalt, iron, nickel, ruthenium or rhodiumto the metal form known to those skilled in the art may be used.

Where promoters, dispersion aids, binders and/or strengthening aids areincorporated in the Fischer-Tropsch synthesis catalyst according to thepresent invention, the addition of these materials may be integrated atseveral stages of the process according to the present invention.Preferably, the promoter, dispersion aids, binder or strengthening aidsare admixed during any stage prior to extrusion, or during theimpregnation step.

The Fischer-Tropsch synthesis catalyst comprising a porous, extrudedtitania-based material according to the present invention or aFischer-Tropsch synthesis catalyst obtainable by a process according tothe present invention will preferably have a crush strength of greaterthan 5.0 lbf, more preferably greater than 7.0 lbf, and even morepreferably greater than 10.0 lbf. The upper limit of the crush strengthof the Fischer-Tropsch synthesis catalyst according to the presentinvention is not particularly critical, but a suitable upper crushstrength is 25.0 lbf. Particularly preferred ranges of crush strengthfor Fischer-Tropsch synthesis catalysts according to the presentinvention are 5.0 lbf to 25.0 lbf, preferably 7.0 lbf to 20.0 lbf, morepreferably 10.0 lbf to 17.0 lbf.

The Fischer-Tropsch synthesis catalyst comprising a porous, extrudedtitania-based material according to the present invention or aFischer-Tropsch synthesis catalyst obtainable by a process according tothe present invention may be used as a catalyst in any conventionalFischer-Tropsch process for converting a mixture of hydrogen and carbonmonoxide gases to hydrocarbons. The Fischer-Tropsch synthesis ofhydrocarbons from a mixture of hydrogen and carbon monoxide, such assyngas, may be represented by Equation 1:

mCO+(2m+1)H₂ →mH₂O+C_(m)H_(2m+2)  Equation 1

As discussed hereinbefore, the Fischer-Tropsch synthesis catalystsaccording to the present invention or obtainable by the process of thepresent invention have improved crush strength and are therefore bettersuited for use in fixed-bed Fischer-Tropsch processes. Additionally,Fischer-Tropsch synthesis catalysts according to the present invention,or obtainable by a process of the present invention, and comprisingmesopores and micropores have been surprisingly found to have improvedcatalyst activity and/or selectivity, particularly reduced selectivityfor methane. The Fischer-Tropsch synthesis catalyst according to thepresent invention, or obtainable by a process according to the presentinvention, therefore provides particularly useful ranges of hydrocarbonswhen used in a Fischer-Tropsch reaction.

A composition according to the present invention comprising hydrocarbonsobtained by a process of the present invention is preferably a fuelcomposition, for example a gasoline, diesel or aviation fuel orprecursor thereof.

The present invention will now be illustrated by way of the followingExamples.

EXAMPLES Comparative Example 1 Titania Extrudate Formed with DistilledWater

Titanium dioxide (BASF P25) was mixed in a mechanical mixer (Vinci MX0.4) with sufficient distilled water to form an extrudable paste, forexample at a water to titanium mass ratio of 0.66 g/g. The resultantpaste was extruded through a die with an array of 1/16 inch circularorifices using a mechanical extruder (Vinci VTE1) to obtain extrudateswith cylindrical shape.

The extrudates were air dried for one hour, then dried at a temperatureof between 100 and 120° C. overnight, followed by calcination in airflow at 500° C. for four hours, via a ramp of 2° C./min.

The mechanical strength of the extrudates was analysed using a VarianBenchsaver™ V200 Tablet Hardness Tester. 50 particles were analysed ineach test, and the mean value was calculated.

The surface area of the extrudates was estimated using the BET model tothe nitrogen adsorption branch of the isotherms collected at 77K on aQuadrasorb SI unit (Quantachrome).

Pore size and pore volume were characterised using mercury porosimetryconducted on an AutoPore IV (Micromeritics) instrument.

Total pore volume was estimated from mercury intrusion volume at 7000psia. Pore size distribution of the sample was calculated using the BJHmodel from desorption isotherms for pore diameters of less than 17 nmand the mercury intrusion profile using the Washburn equation with acontact angle of 130° and a surface tension of bulk mercury of 485 mN/mfor pore diameters of greater than 17 nm.

The physical properties of the extrudates were as follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: 4.7 lbf    -   BET surface area: 51 m²/g    -   Pore volume: 0.36 ml/g    -   Mean pore diameter: 33 nm

Example 1 Titania Extrudate Prepared using 0.2 mol/L TetramethylammoniumHydroxide

The procedure of Comparative Example 1 was repeated, with the exceptionthat the distilled water was replaced by a 0.2 mol/L, aqueous solutionof tetramethylammonium hydroxide (Aldrich).

The physical properties of the extrudates of Example 1 were determinedas set out in Comparative Example 1, and the results are as follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: 10.2 lbf    -   BET surface area: 54 m²/g    -   Pore volume: 0.30 ml/g    -   Mean pore diameter: 24 nm

Compared with the pure titanic extrudates prepared in ComparativeExample 1, the extrudates of Example 1 prepared using 0.2 mol/Ltetramethylammonium hydroxide exhibited substantially higher mechanicalstrength.

Example 2 Titania Extrudate Prepared using 0.5 mol/L TetramethylammoniumHydroxide

The procedure of Comparative Example 1 was repeated, with the exceptionthat the distilled water was replaced by 0.5 mol/L aqueous solution oftetramethylammonium hydroxide.

The physical properties of the extrudates of Example 2 were determinedas set out in Comparative Example 1, and the results are as follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: 11.8 lbf    -   BET surface area: 45 m²/g    -   Pore volume: 0.26 ml/g    -   Mean pore diameter: 24 nm

Example 3 Titanic Extrudate Prepared using 1.0 mol/L TetramethylammoniumHydroxide

The procedure of Comparative Example 1 was repeated, with the exceptionthat the distilled water was replaced by 1.0 mol/L aqueous solution oftetramethylammonium hydroxide.

The physical properties of the extrudates of Example 3 were determinedas set out in Comparative Example 1, and the results are as follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: 30.2 lbf    -   BET surface area: 39 m²/g    -   Pore volume: 0.19 ml/g    -   Mean pore diameter: 12.3 nm

A comparison of the results of Examples 1 to 3 with the results ofComparative Example 1 shows that the use of tetramethylammoniumhydroxide to bind the particles of titanium dioxide before extrusionresulted in an increase in crush strength, with increases in theconcentration of tetramethylammonium hydroxide increasing the crushstrength.

Example 4 Titanic Extrudate Prepared using 0.5 mol/L TetraethylammoniumHydroxide

The procedure of Example 2 was repeated, with the exception that the 0.5mol/L aqueous solution of tetramethylammonium hydroxide was replaced bya 0.5 mol/L aqueous solution of tetraethylammonium hydroxide (Aldrich).

The physical properties of the extrudates of Example 4 were determinedas set out in Comparative Example 1, and the results are as follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: 15.9 lbf    -   BET surface area: 40.2 m²/g    -   Pore volume: 0.14 ml/g    -   Mean pore diameter: 10.0 nm

Example 5 Titania Extrudate Prepared using 0.5 mol/L TetrapropylammoniumHydroxide

The procedure of Example 2 was repeated, with the exception that the 0.5mol/L aqueous solution of tetramethylammonium hydroxide was replaced bya 0.5 mol/L aqueous solution of tetrapropylammonium hydroxide (Aldrich).

The physical properties of the extrudates of Example 5 were determinedas set out in Comparative Example 1, and the results are as follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: 14.0 lbf    -   BET surface area: 42.1 m²/g    -   Pore volume: 0.15 ml/g    -   Mean pore diameter: 13.1

Example 6 Titania Extrudate Prepared using 0.5 mol/L TetrabutylammoniumHydroxide

The procedure of Example 2 was repeated, with the exception that the 0.5mol/L aqueous solution of tetramethylammonium hydroxide was replaced bya 0.5 mol/L aqueous solution of tetrabutylammonium hydroxide (Aldrich).

The physical properties of the extrudates of Example 6 were determinedas set out in Comparative Example 1, and the results are as follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: 16.0 lbf    -   BET surface area: 40.6 m²/g    -   Pore volume: 0.15 ml/g    -   Mean pore diameter: 13.1

A comparison of the results of Examples 4 to 6 with the results ofComparative Example 1 and the results of Examples 1 to 3 demonstratethat the mechanical strength of titania extrudates may be substantiallyimproved by using alternative quaternary ammonium hydroxide compounds.

Comparative Example 2 Titania Extrudate Comprising Mesopores andMacropores Prepared using a Cellulose Porogen and Formed with DistilledWater

Titanium dioxide (Evonik P25) was mixed with cellulose fibre (CF,Aldrich) at a cellulose fibre:titanium dioxide ratio of 0.5 g/g and themixture was homogenised using a 360° rotating mixer (Turbula). Themixture was then formulated in a pilot plant scale mechanical mixer(Simpson Muller) with sufficient deionised water to form an extrudablepaste. The resultant paste was extruded through a die with an array of1/16 inch circular orifices using a pilot plant scale extruder (Bonnet)to obtain extrudates with cylindrical shape. The extrudates were driedand calcined as set out in Comparative Example 1.

The physical properties of the dried and calcined extrudates ofComparative Example 2 were determined as set out in Comparative Example1, and the results are as follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: Less than 1.0 lbf (below the detection limit of        the instrument)    -   BET surface area: 47.3 m²/g    -   Pore volume: 0.52 ml/g    -   Mean pore diameter: bi-modal distribution, centred at 30.2 nm        and 124.9 nm, respectively.

Example 7 Titania Extrudate Comprising Mesopores and Macropores Preparedusing a Cellulose Porogen and 0.5 mol/L Tetramethylammonium Hydroxide

The procedure of Comparative Example 2 was repeated, with the exceptionthat the deionized water was replaced by a 0.5 mol/L aqueous solution oftetramethylammonium hydroxide. The extrudates of Example 7 werecharacterised as set out in Comparative Example 1, and the results areas follows:

-   -   Geometry: 1/16 inch diameter cylinder    -   Crush strength: 7.2 lbf    -   BET surface area: 46.5 m²/g    -   Pore volume: 0.44 ml/g    -   Mean pore diameter/distribution: bi-modal distribution, centred        at 19.1 nm and 60.3 nm, respectively.

Example 8 Titania Extrudates Prepared using 0.5 mol/LTetramethylammonium Hydroxide

The procedure of Example 7 was repeated, with the exception that thehomogenized paste was extruded through an array of 1/16 inch cylindricaltrilobe orifices to obtain extrudates with cylindrical trilobe geometry.The extrudates were dried and calcined, and subsequently characterised,as set out in Comparative Example 1, and the results are as follows:

-   -   Geometry: 1/16 inch diameter trilobe    -   Crush strength: 9.7 lbf    -   BET surface area: 46.8 m²/g    -   Pore volume: 0.44 ml/g    -   Mean pore diameter/distribution: bi-modal distribution, centred        at 20.1 nm and 60.3 nm, respectively.

A comparison of the results of Comparative Example 2 and Examples 7 and8 demonstrates that the mechanical strength (crush strength) of titaniaextrudates comprising micropores and macropores may also besubstantially improved by using a quaternary ammonium hydroxide solutionduring the formulation of the homogeneous paste to be extruded, and alsothat the improved crush strength is maintained in different extrudategeometries.

The dimensions and values disclosed herein are not to be understood asbeing strictly limited to the exact numerical values recited. Instead,unless otherwise specified, each such dimension is intended to mean boththe recited value and a functionally equivalent range surrounding thatvalue. For example, a dimension disclosed as “40 mm” is intended to mean“about 40 mm.”

Every document cited herein, including any cross referenced or relatedpatent or application, is hereby incorporated herein by reference in itsentirety unless expressly excluded or otherwise limited. The citation ofany document is not an admission that it is prior art with respect toany invention disclosed or claimed herein or that it alone, or in anycombination with any other reference or references, teaches, suggests ordiscloses any such invention. Further, to the extent that any meaning ordefinition of a term in this document conflicts with any meaning ordefinition of the same term in a document incorporated by reference, themeaning or definition assigned to that term in this document shallgovern.

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope and spirit of this invention.

1. A porous, extruded titania-based material further comprising one ormore quaternary ammonium compounds.
 2. A porous, extruded titania-basedmaterial according to claim 1, in the form of symmetrical cylinders,dilobes, trilobes, quadralobes or hollow cylinders.
 3. A porous,extruded titania-based material according to claim 1, having a crushstrength of greater than 3.0 lbf, preferably greater than 5.0 lbf.
 4. Aporous, extruded titania-based material according to claim 1, whereinthe one or more quaternary ammonium compounds comprisestetramethylammonium hydroxide, tetraethylammonium hydroxide,tetrapropylammonium hydroxide, tetrabutylammonium hydroxide orcetyltrimethylammonium hydroxide.
 5. A porous, extruded titania-basedmaterial according to claim 1, comprising mesopores and macropores.
 6. Aporous, extruded titania-based material according to claim 5, whereinthe mesopores have a pore diameter of 2 to 50 nm, preferably 15 to 45 nmor 30 to 45 nm, more preferably 25 to 40 nm or 30 to 40 nm.
 7. A porous,extruded titania-based material according to claim 5, wherein themacropores have a pore diameter of greater than 50 nm, preferably 60 to1000 nm, more preferably 100 to 850 nm.
 8. A porous, extrudedtitania-based material according to claim 5, wherein the total porevolume is at least 0.3 ml/g, preferably at least 0.40 ml/g.
 9. A porous,extruded titania-based material according to claim 5, wherein thesurface area is at least 30 m²/g, preferably at least 40 m²/g.
 10. Aprocess for the preparation of a porous, extruded titania-based materialhaving a crush strength greater than 3.0 lbf, said process comprising:a) mixing titanium dioxide and a solution of one or more quaternaryammonium compounds to form a homogenous paste; b) extruding the paste toform an extrudate; and c) drying and/or calcining the extrudate.
 11. Aprocess according to claim 10, wherein the solution of one or morequaternary ammonium compounds comprises tetramethylammonium hydroxide,tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide or cetyltrimethylammonium hydroxide.
 12. Aporous, extruded titania-based material obtainable by the process ofclaim
 10. 13. A process for the preparation of a porous, extrudedtitania-based material comprising mesopores and macropores and having acrush strength greater than 3.0 lbf, said process comprising: a) mixingtitanium dioxide and one or more porogens to form a homogenous mixture;b) adding a solution of one or more quaternary ammonium compounds to thehomogenous mixture, and mixing to form a homogenous paste; c) extrudingthe paste to form an extrudate; and d) drying and/or calcining theextrudate at a temperature sufficient to decompose the one or moreporogens.
 14. A process according to claim 13, wherein the solution ofone or more quaternary ammonium compounds comprises tetramethylammoniumhydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide or cetyltrimethylammonium hydroxide.
 15. Aprocess according to claim 13, wherein the one or more porogen comprisescellulose or a derivative thereof, such as methyl cellulose, ethylcellulose and ethyl methyl cellulose; alginic acid or a derivativethereof, such as ammonium alginate, sodium alginate and calciumalginate; latex or polyvinyl chloride.
 16. A process according to claim13, wherein the weight ratio of titanium dioxide to porogen is from1:0.1 to 1:1.0, preferably 1:0.1 to 1:0.8, more preferably 1:0.15 to1:0.6.
 17. A porous, extruded titania-based material obtainable by aprocess according to claim
 13. 18. A Fischer-Tropsch synthesis catalystcomprising a porous, extruded titania-based material according to claim1, and further comprising at least one metal selected from cobalt, iron,nickel, ruthenium or rhodium.
 19. A Fischer-Tropsch synthesis catalystcomprising a porous, extruded titania-based material according to claim5, and further comprising at least one metal selected from cobalt, iron,nickel, ruthenium or rhodium.
 20. A Fischer-Tropsch synthesis catalystaccording to claim 18, further comprising one or more promoters,preferably wherein the one or more promoters are selected from rhenium,ruthenium, platinum, palladium, molybdenum, tungsten, boron, zirconium,gallium, thorium, manganese, lanthanum, cerium or mixtures thereof. 21.A process for the preparation of a Fischer-Tropsch synthesis catalystaccording to claim 18, said process comprising: a) mixing titaniumdioxide, a solution of one or more quaternary ammonium compounds and asolution of at least one thermally decomposable cobalt, iron, nickel,ruthenium or rhodium compound, to form a homogenous paste; b) extrudingthe paste to form an extrudate; c) drying and/or calcining the extrudateat a temperature sufficient to convert the one or more thermallydecomposable cobalt, iron, nickel, ruthenium or rhodium compound to anoxide thereof or to the metal form; and, where an oxide is formed,optionally d) heating the dried and/or calcined extrudate under reducingconditions to convert the one or more cobalt, iron, nickel, ruthenium orrhodium oxide to the metal form.
 22. A process for the preparation of aFischer-Tropsch synthesis catalyst according to claim 19, said processcomprising: a) mixing titanium dioxide and one or more porogens to forma homogenous mixture; b) adding a solution of one or more quaternaryammonium compounds and a solution of at least one thermally decomposablecobalt, iron, nickel, ruthenium or rhodium compound to the mixture, andmixing to form a homogenous paste; c) extruding the paste to form anextrudate; d) drying and/or calcining the extrudate at a temperaturesufficient to decompose the one or more porogens and to convert the atleast one thermally decomposable cobalt, iron, nickel, ruthenium orrhodium compound to an oxide thereof, or to the metal form; and, wherean oxide is formed, optionally e) heating the dried and/or calcinedextrudate under reducing conditions to convert the one or more cobalt,iron, nickel, ruthenium or rhodium oxide to the metal form.
 23. Aprocess according to claim 21, wherein the solution of one or morequaternary ammonium compounds comprises tetramethylammonium hydroxide,tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide or cetyltrimethylammonium hydroxide.
 24. Aprocess for the preparation of a Fischer-Tropsch synthesis catalystaccording to claim 18, said process comprising: a) impregnating aporous, extruded titania-based material with a solution of at least onethermally decomposable cobalt, iron, nickel, ruthenium or rhodiumcompound; b) drying and/or calcining the impregnated porous, extrudedtitania-based material at a temperature sufficient to convert the atleast one thermally decomposable cobalt, iron, nickel, ruthenium orrhodium compound to an oxide thereof or to the metal form; and where anoxide is formed, optionally c) heating the dried and/or calcined porous,extruded titania-based material under reducing conditions to convert theat least one cobalt, iron, nickel, ruthenium or rhodium oxide to themetal form.
 25. A Fischer-Tropsch synthesis catalyst obtainable by theprocess of claim 21, preferably having a crush strength of greater than5.0 lbf.
 26. (canceled)
 27. (canceled)
 28. (canceled)
 29. (canceled) 30.A process for converting a mixture of hydrogen and carbon monoxide gasesto hydrocarbons, which process comprises contacting a mixture ofhydrogen and carbon monoxide with a Fischer-Tropsch synthesis catalystaccording to claim
 18. 31. A composition, preferably a fuel composition,comprising hydrocarbons obtained by a process according to claim
 30. 32.A process for producing a fuel composition, said process comprisingblending hydrocarbons obtained by a process according to claim 30 withone or more fuel components to form the fuel composition.